I got a email back from Frank..I’m not blit waiting plane to plane. I’m assuming the blitter will hog the bus and lock out the CPU while it is active. It's a bit nasty and it is relying on timing of the CPU/blitter.

So one of those "timing dependent" things (like raster etc) it seems. So all is well again

Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.

One thing I noticed the other day which I need to look at the bit more.. Was that HD10.01 driver crashed on boot up in 40MHz mode. I am not sure if anything else was loading in the AUTO folder.. I need to check will not had chance yet..

Basically when HD10 loaded it would bomb out. You'll thing is if I booted in 8MHz mode it would all load fine, and then the driver seemed to work fine in switching back to 40MHz mode. I emailed Uwe about it, he says it works on other machines like the Milan etc and that there is no timing dependent code in HD10..

So if any of you guys with this booster can try it out, really just load the driver from the floppy, and see if it bombs on boot or not.. I will try and do this myself bought I'm going to be busy today some other stuff..